1. Technical Field
The present invention generally relates to alignment, positioning, attachment and connection of optical fibers to other components and more specifically to devices incorporating fiber bragg gratings.
2. Discussion
A fiber bragg grating device consists of an optical fiber having a periodic stack of regions with higher and lower refractive indexes. With this configuration, light within a narrow band of wavelengths is reflected while all wavelengths outside that band are transmitted. One critical aspect of fiber bragg grating devices is the period at which the higher and lower refractive index regions change with temperature.
Conventional bragg grating devices compensate for thermal drift and refractive index changes by mounting the fiber under tension on a negative thermal expansion substrate. The fiber is mounted to the substrate by way of a glass frit. Glass frits are advantageous since they exhibit little or no creep. However, glass frits also have certain drawbacks.
For example, a significant problem associated with glass frits results from the high temperatures required for attachment. That is, cooling of the frit results in large stresses on the assembly due to the thermal expansion mismatch between the frit, fiber, and substrate. Additionally, high temperatures have been shown to degrade certain types of negative expansion substrates, cause CWL drift, grating fade, and decrease fiber tensile strength.
One theory for overcoming the above-identified problems is to attach the fiber to the substrate at a temperature near the operating temperature of the assembly such that the effect of the thermal expansion mismatch is minimized. Adhesive polymers have been considered for such use. However, polymers exhibit significant creep which is detrimental to the performance of the fiber bragg grating device.
In view of the foregoing, it would be desirable to provide an apparatus for attaching a fiber to a substrate such as those used in fiber bragg grating devices which overcomes the problems associated with the prior art.
The above and other objects are provided by mechanically attaching the fiber to the substrate such that no chemical bond is made with the fiber and only frictional forces from an applied radial force hold the fiber in place. The mechanical attachment is made at ambient temperatures such that the thermal expansion mismatch of the materials used is not a concern. The apparatus preferably includes a clamping block formed of malleable material disposed adjacent substrate. An optical fiber is disposed adjacent the clamping block and a securing member such as a fastener or spring is used to secure the fiber to the clamping block substrate. The frictional forces between the fiber and the clamping block eliminate movement of the fiber relative to the substrate.